1. Field of the Invention
The present invention relates to a reversible thermosensitive recording material capable of recording and erasing images repeatedly by utilizing its property that the transparency can be changed reversibly from a transparent state to an opaque state, and vice versa, depending upon the temperature thereof, and a method for producing the above-mentioned reversible thermosensitive recording material.
2. Discussion of Background
Recently attention has been paid to a reversible thermosensitive recording material capable of temporarily recording images thereon and erasing the same therefrom when such images become unnecessary. For example, as disclosed in Japanese Laid-Open Patent Applications 54-119377, 55-154198, 63-39376 and 63-107584, there are conventionally known reversible thermosensitive recording materials in which an organic low-molecular-weight material such as a higher fatty acid is dispersed in a matrix resin such as a vinyl chloride - vinyl acetate resin with a glass transition temperature (Tg) of as low as 50.degree. C. or more to less than 80.degree. C.
In the case where only heat energy is applied to a reversible thermosensitive recording material by using a heat-application roller or a heat-pen, with the application of slight pressure thereto, in order to perform recording and erasing operations, the durability of the recording material is not degraded even though the image formation and erasure are repeated. However, when both heat and pressure are repeatedly applied to the recording material at the same time for image recording and erasing, for instance, by using a thermal head, the matrix resin enclosing domains of the organic low-molecular-weight material is deformed in the reversible thermosensitive recording layer, so that the domains of the low-molecular-weight material which are discretely dispersed in the matrix resin at the initial stage are apt to coalesce. The size of each domain of the low-molecular-weight material is thus increased, with the result that the light scattering effect of the recording layer is decreased, and the degree of whiteness of the milky white opaque area in the recording layer is undesirably degraded. Finally the image quality and the contrast are lowered.